(1) Field of the Invention
The present invention generally relates to methods for altering and cutting circuit patterns of a printed-circuit board and a printed-circuit board, and more particularly to an altering method for altering a circuit pattern on an inner layer of a multi-layer printed-circuit board (an organic printed-circuit board, such as a glass-epoxy board and a polyimide board, and an inorganic printed-circuit board, such as a ceramic board), a cutting method for cutting a circuit pattern of a printed-circuit board, applicable to the altering method, and a printed-circuit board having an altered circuit pattern.
(2) Description of the Related Art
Conventionally, in a printed-circuit board in which a circuit pattern corresponding to electronic circuits for electronic equipment is formed, spare circuit lines, spare connecting pads, spare via-holes used to electrically connecting circuit patterns on stacked layers and the like are often additionally formed for alteration of the circuit pattern based on design changes of the electronic circuits. When the design changes of the electronic circuits have been made, a new circuit pattern can be formed using the spare circuit lines, the spare connecting pads and the spare via-holes. In addition, the circuit pattern corresponding to the original electronic circuits is cut so as to be altered into a circuit pattern corresponding to the design changed electronic circuits.
Due to the use of such printed-circuit boards, even if the design changes of the electronic circuits are made, it is not necessary to make a new printed-circuit board corresponding to the design changed electronic circuits. Thus, the printed-circuit board having the circuit pattern corresponding to the design changed circuits can be rapidly prepared.
On the other hand, in recent years, printed-circuit boards have been miniaturized by increasing the density of the circuit pattern. Thus, since forming of the spare circuit lines, the spare connecting pads and the spare via-holes prevents the density of the circuit pattern from being increased, there is a tendency to abandon formation of these spare elements.
However, in a case where a printed-circuit board from which the spare elements, such as the spare circuit lines, the spare connecting pads and the spare via-holes are omitted is used, it is difficult to alter a circuit pattern on an inner layer of the printed-circuit board when the design changes of the electronic circuits have been made.
In addition, in a case where the circuit pattern on the inner layer of the printed-circuit board is altered, the circuit pattern is generally cut. In this case, the circuit pattern on the inner layer of the printed-circuit board has to be accurately cut with consideration to a position of an adjacent circuit pattern. In particular, in a case where the circuit is cut, in a non-contacting manner, using a high energy beam, such as an electron beam or a laser beam, metal powder generated by the abrasion of material of the circuit pattern causes insulation defects. The insulation defects must be prevented.
Accordingly, a general object of the present invention is to provide methods for altering and cutting a circuit pattern of a printed-circuit board and a printed-circuit board having an altered circuit pattern, in which the disadvantages of the aforementioned prior art are eliminated.
A first specific object of the present invention is to provide an altering method which can easily alter a circuit pattern on an inner layer of a printed-circuit board.
The above objects of the present invention are achieved by a method for altering a circuit pattern of a printed-circuit board, comprising the steps of: (a) removing a portion of the printed-circuit board so that the circuit pattern inside the printed-circuit board is exposed; and (b) connecting an exposed portion of the circuit pattern obtained in step (a) to another portion of the printed-circuit board by a conductive body so that a circuit path is formed between the exposed portion of the circuit pattern and the another portion of the printed-circuit board.
According to the altering method of the present invention, a new circuit path which connects the circuit pattern to another portion of the printed-circuit board can be formed without spare circuit lines, spare lands and the like.
A second specific object of the present invention is to provide a cutting method by which a circuit pattern can be accurately cut in consideration of a position of another circuit pattern.
The above object of the present invention is achieved by the following methods:
A method for cutting a circuit pattern located under a sheet-shaped circuit pattern inside a printed-circuit board comprising the steps of (a) forming a first cutting hole which passes through the sheet-shaped circuit pattern, the first cutting hole having a first aperture area, and (b) forming a second cutting hole which expands from a bottom surface of the first cutting hole and passes through the circuit pattern so that the circuit pattern is cut, the second cutting hole having a second aperture area narrower than the first aperture area;
A method for cutting a circuit pattern inside a printed-circuit board comprising the steps of (a) removing a portion with a predetermined depth of the printed-circuit board, and (b) expanding the portion which is removed in a direction parallel to the surface of the printed-circuit board, so that the circuit pattern is cut while the portion which is removed is being expanded;
A method for cutting a circuit pattern inside a printed-circuit board comprising the steps of (a) adjusting a mask of a beam so that a projection area of the beam projected onto a surface of the printed-circuit board has a predetermined length in a direction parallel to a width direction of the circuit pattern, and (b) projecting the beam onto the printed-circuit board so that a hole is formed in the printed-circuit board, whereby the circuit pattern is cut by the beam;
A method for cutting a circuit pattern inside a printed-circuit board comprising the steps of (a) adjusting a mask of a beam having a predetermined energy so that a projection area of the beam is formed on a surface of the printed-circuit board, the projection area being decided based on a narrowing ratio of the beam and a working area of the beam projected onto a surface of the circuit pattern to be cut, the narrowing ratio of the beam being a degree of narrowing of an area, to be worked by the beam having the predetermined energy, in materials on and over a surface of the circuit pattern, and (b) projecting the beam in which the mask thereof is adjusted on the printed circuit board so that a hole is formed in the printed-circuit board, whereby the circuit pattern is cut by the beam;
A method for cutting a circuit pattern inside a printed-circuit board comprising the steps of (a) removing a portion of the printed-circuit board by projection of a beam focused on a focal point, and (b) moving the focal point on which the beam is focused with moving of a working area of the beam inside the printed-circuit board caused by removal of the portion of the printed-circuit board, whereby the circuit pattern is cut by the beam;
A method for cutting a circuit pattern inside a printed-circuit board comprising the steps of (a) projecting a beam in which a mask thereof is adjusted so that a first projection area of the beam corresponds to an area covering the circuit pattern, a first portion at a first side of the circuit pattern and a second portion at a second side of the circuit pattern, a hole being formed by the beam until a predetermined depth is obtained, (b) projecting the beam in which the mask thereof is adjusted so that a second projection area of the beam corresponds to an area covering the circuit pattern and the first portion, and (c) projecting the beam in which the mask thereof is adjusted so that a third projection area of the beam corresponds to an area covering the circuit pattern and the second portion, wherein after the step (a) is completed, the step (b) and the step (c) are alternately repeated at predetermined intervals until the circuit pattern is cut by the beam; and
A method for cutting a circuit pattern inside a printed-circuit board comprising the step of projecting a beam on the printed-circuit board while a mask thereof is being adjusted so that a projection area of the beam is narrowed, a hole being formed in the printed-circuit board by projection of the beam, so that the circuit pattern is cut by the beam.
According to the cutting method of the present invention, the circuit pattern can be accurately cut while taking into consideration of a position of another circuit pattern such as the sheet-shaped circuit pattern.
A third specific object of the present invention is to provide a printed-circuit board having an altered circuit pattern.
The above object of the present invention is achieved by a printed-circuit board comprising: a circuit device mounted on the printed circuit board; and a conductive body which is in a groove formed in the printed-circuit board so as to pass under the circuit device, the groove corresponding to a circuit path.
According to the printed-circuit board of the present invention, the printed-circuit board in which a circuit pattern has been altered can be obtained.